/*
 * Copyright (c) 1991, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *	@(#)queue.h	8.5 (Berkeley) 8/20/94
 */

#ifndef _SYS_QUEUE_H_
#define _SYS_QUEUE_H_

/*
 * This file defines five types of data structures: singly-linked lists,
 * lists, simple queues, tail queues, and circular queues.
 *
 * A singly-linked list is headed by a single forward pointer. The
 * elements are singly linked for minimum space and pointer manipulation
 * overhead at the expense of O(n) removal for arbitrary elements. New
 * elements can be added to the list after an existing element or at the
 * head of the list.  Elements being removed from the head of the list
 * should use the explicit macro for this purpose for optimum
 * efficiency. A singly-linked list may only be traversed in the forward
 * direction.  Singly-linked lists are ideal for applications with large
 * datasets and few or no removals or for implementing a LIFO queue.
 *
 * A list is headed by a single forward pointer (or an array of forward
 * pointers for a hash table header). The elements are doubly linked
 * so that an arbitrary element can be removed without a need to
 * traverse the list. New elements can be added to the list before
 * or after an existing element or at the head of the list. A list
 * may only be traversed in the forward direction.
 *
 * A simple queue is headed by a pair of pointers, one the head of the
 * list and the other to the tail of the list. The elements are singly
 * linked to save space, so elements can only be removed from the
 * head of the list. New elements can be added to the list after
 * an existing element, at the head of the list, or at the end of the
 * list. A simple queue may only be traversed in the forward direction.
 *
 * A tail queue is headed by a pair of pointers, one to the head of the
 * list and the other to the tail of the list. The elements are doubly
 * linked so that an arbitrary element can be removed without a need to
 * traverse the list. New elements can be added to the list before or
 * after an existing element, at the head of the list, or at the end of
 * the list. A tail queue may be traversed in either direction.
 *
 * A circle queue is headed by a pair of pointers, one to the head of the
 * list and the other to the tail of the list. The elements are doubly
 * linked so that an arbitrary element can be removed without a need to
 * traverse the list. New elements can be added to the list before or after
 * an existing element, at the head of the list, or at the end of the list.
 * A circle queue may be traversed in either direction, but has a more
 * complex end of list detection.
 *
 * For details on the use of these macros, see the queue(3) manual page.
 */

/*
 * Simple queue definitions.
 */
#define SIMPLEQ_HEAD(name, type)                                               \
    struct name {                                                              \
        struct type *sqh_first; /* first element */                            \
        struct type **sqh_last; /* addr of last next element */                \
    }

#define SIMPLEQ_HEAD_INITIALIZER(head)                                         \
    {                                                                          \
        NULL, &(head).sqh_first                                                \
    }

#define SIMPLEQ_ENTRY(type)                                                    \
    struct {                                                                   \
        struct type *sqe_next; /* next element */                              \
    }

/*
 * Simple queue functions.
 */
#define SIMPLEQ_INIT(head)                                                     \
    do {                                                                       \
        (head)->sqh_first = NULL;                                              \
        (head)->sqh_last = &(head)->sqh_first;                                 \
    } while (/*CONSTCOND*/ 0)

#define SIMPLEQ_INSERT_HEAD(head, elm, field)                                  \
    do {                                                                       \
        if (((elm)->field.sqe_next = (head)->sqh_first) == NULL)               \
            (head)->sqh_last = &(elm)->field.sqe_next;                         \
        (head)->sqh_first = (elm);                                             \
    } while (/*CONSTCOND*/ 0)

#define SIMPLEQ_INSERT_TAIL(head, elm, field)                                  \
    do {                                                                       \
        (elm)->field.sqe_next = NULL;                                          \
        *(head)->sqh_last = (elm);                                             \
        (head)->sqh_last = &(elm)->field.sqe_next;                             \
    } while (/*CONSTCOND*/ 0)

#define SIMPLEQ_INSERT_AFTER(head, listelm, elm, field)                        \
    do {                                                                       \
        if (((elm)->field.sqe_next = (listelm)->field.sqe_next) == NULL)       \
            (head)->sqh_last = &(elm)->field.sqe_next;                         \
        (listelm)->field.sqe_next = (elm);                                     \
    } while (/*CONSTCOND*/ 0)

#define SIMPLEQ_REMOVE_HEAD(head, field)                                       \
    do {                                                                       \
        if (((head)->sqh_first = (head)->sqh_first->field.sqe_next) == NULL)   \
            (head)->sqh_last = &(head)->sqh_first;                             \
    } while (/*CONSTCOND*/ 0)

#define SIMPLEQ_REMOVE(head, elm, type, field)                                 \
    do {                                                                       \
        if ((head)->sqh_first == (elm)) {                                      \
            SIMPLEQ_REMOVE_HEAD((head), field);                                \
        } else {                                                               \
            struct type *curelm = (head)->sqh_first;                           \
            while (curelm->field.sqe_next != (elm))                            \
                curelm = curelm->field.sqe_next;                               \
            if ((curelm->field.sqe_next =                                      \
                     curelm->field.sqe_next->field.sqe_next) == NULL)          \
                (head)->sqh_last = &(curelm)->field.sqe_next;                  \
        }                                                                      \
    } while (/*CONSTCOND*/ 0)

#define SIMPLEQ_FOREACH(var, head, field)                                      \
    for ((var) = ((head)->sqh_first); (var); (var) = ((var)->field.sqe_next))

/*
 * Simple queue access methods.
 */
#define SIMPLEQ_EMPTY(head)      ((head)->sqh_first == NULL)
#define SIMPLEQ_FIRST(head)      ((head)->sqh_first)
#define SIMPLEQ_NEXT(elm, field) ((elm)->field.sqe_next)

/*
 * Tail queue definitions.
 */
#define _TAILQ_HEAD(name, type, qual)                                          \
    struct name {                                                              \
        qual type *tqh_first;      /* first element */                         \
        qual type *qual *tqh_last; /* addr of last next element */             \
    }
#define TAILQ_HEAD(name, type) _TAILQ_HEAD(name, struct type, )

#define TAILQ_HEAD_INITIALIZER(head)                                           \
    {                                                                          \
        NULL, &(head).tqh_first                                                \
    }

#define _TAILQ_ENTRY(type, qual)                                               \
    struct {                                                                   \
        qual type *tqe_next;       /* next element */                          \
        qual type *qual *tqe_prev; /* address of previous next element */      \
    }
#define TAILQ_ENTRY(type) _TAILQ_ENTRY(struct type, )

/*
 * Tail queue functions.
 */
#define TAILQ_INIT(head)                                                       \
    do {                                                                       \
        (head)->tqh_first = NULL;                                              \
        (head)->tqh_last = &(head)->tqh_first;                                 \
    } while (/*CONSTCOND*/ 0)

#define TAILQ_INSERT_HEAD(head, elm, field)                                    \
    do {                                                                       \
        if (((elm)->field.tqe_next = (head)->tqh_first) != NULL)               \
            (head)->tqh_first->field.tqe_prev = &(elm)->field.tqe_next;        \
        else                                                                   \
            (head)->tqh_last = &(elm)->field.tqe_next;                         \
        (head)->tqh_first = (elm);                                             \
        (elm)->field.tqe_prev = &(head)->tqh_first;                            \
    } while (/*CONSTCOND*/ 0)

#define TAILQ_INSERT_TAIL(head, elm, field)                                    \
    do {                                                                       \
        (elm)->field.tqe_next = NULL;                                          \
        (elm)->field.tqe_prev = (head)->tqh_last;                              \
        *(head)->tqh_last = (elm);                                             \
        (head)->tqh_last = &(elm)->field.tqe_next;                             \
    } while (/*CONSTCOND*/ 0)

#define TAILQ_INSERT_AFTER(head, listelm, elm, field)                          \
    do {                                                                       \
        if (((elm)->field.tqe_next = (listelm)->field.tqe_next) != NULL)       \
            (elm)->field.tqe_next->field.tqe_prev = &(elm)->field.tqe_next;    \
        else                                                                   \
            (head)->tqh_last = &(elm)->field.tqe_next;                         \
        (listelm)->field.tqe_next = (elm);                                     \
        (elm)->field.tqe_prev = &(listelm)->field.tqe_next;                    \
    } while (/*CONSTCOND*/ 0)

#define TAILQ_INSERT_BEFORE(listelm, elm, field)                               \
    do {                                                                       \
        (elm)->field.tqe_prev = (listelm)->field.tqe_prev;                     \
        (elm)->field.tqe_next = (listelm);                                     \
        *(listelm)->field.tqe_prev = (elm);                                    \
        (listelm)->field.tqe_prev = &(elm)->field.tqe_next;                    \
    } while (/*CONSTCOND*/ 0)

#define TAILQ_REMOVE(head, elm, field)                                         \
    do {                                                                       \
        if (((elm)->field.tqe_next) != NULL)                                   \
            (elm)->field.tqe_next->field.tqe_prev = (elm)->field.tqe_prev;     \
        else                                                                   \
            (head)->tqh_last = (elm)->field.tqe_prev;                          \
        *(elm)->field.tqe_prev = (elm)->field.tqe_next;                        \
    } while (/*CONSTCOND*/ 0)

#define TAILQ_FOREACH(var, head, field)                                        \
    for ((var) = ((head)->tqh_first); (var); (var) = ((var)->field.tqe_next))

#define TAILQ_FOREACH_REVERSE(var, head, headname, field)                      \
    for ((var) = (*(((struct headname *)((head)->tqh_last))->tqh_last));       \
         (var);                                                                \
         (var) = (*(((struct headname *)((var)->field.tqe_prev))->tqh_last)))

#define TAILQ_CONCAT(head1, head2, field)                                      \
    do {                                                                       \
        if (!TAILQ_EMPTY(head2)) {                                             \
            *(head1)->tqh_last = (head2)->tqh_first;                           \
            (head2)->tqh_first->field.tqe_prev = (head1)->tqh_last;            \
            (head1)->tqh_last = (head2)->tqh_last;                             \
            TAILQ_INIT((head2));                                               \
        }                                                                      \
    } while (/*CONSTCOND*/ 0)

/*
 * Tail queue access methods.
 */
#define TAILQ_EMPTY(head)      ((head)->tqh_first == NULL)
#define TAILQ_FIRST(head)      ((head)->tqh_first)
#define TAILQ_NEXT(elm, field) ((elm)->field.tqe_next)

#define TAILQ_LAST(head, headname)                                             \
    (*(((struct headname *)((head)->tqh_last))->tqh_last))
#define TAILQ_PREV(elm, headname, field)                                       \
    (*(((struct headname *)((elm)->field.tqe_prev))->tqh_last))

/*
 * Circular queue definitions.
 */
#define CIRCLEQ_HEAD(name, type)                                               \
    struct name {                                                              \
        struct type *cqh_first; /* first element */                            \
        struct type *cqh_last;  /* last element */                             \
    }

#define CIRCLEQ_HEAD_INITIALIZER(head)                                         \
    {                                                                          \
        (void *)&head, (void *)&head                                           \
    }

#define CIRCLEQ_ENTRY(type)                                                    \
    struct {                                                                   \
        struct type *cqe_next; /* next element */                              \
        struct type *cqe_prev; /* previous element */                          \
    }

/*
 * Circular queue functions.
 */
#define CIRCLEQ_INIT(head)                                                     \
    do {                                                                       \
        (head)->cqh_first = (void *)(head);                                    \
        (head)->cqh_last = (void *)(head);                                     \
    } while (/*CONSTCOND*/ 0)

#define CIRCLEQ_INSERT_AFTER(head, listelm, elm, field)                        \
    do {                                                                       \
        (elm)->field.cqe_next = (listelm)->field.cqe_next;                     \
        (elm)->field.cqe_prev = (listelm);                                     \
        if ((listelm)->field.cqe_next == (void *)(head))                       \
            (head)->cqh_last = (elm);                                          \
        else                                                                   \
            (listelm)->field.cqe_next->field.cqe_prev = (elm);                 \
        (listelm)->field.cqe_next = (elm);                                     \
    } while (/*CONSTCOND*/ 0)

#define CIRCLEQ_INSERT_BEFORE(head, listelm, elm, field)                       \
    do {                                                                       \
        (elm)->field.cqe_next = (listelm);                                     \
        (elm)->field.cqe_prev = (listelm)->field.cqe_prev;                     \
        if ((listelm)->field.cqe_prev == (void *)(head))                       \
            (head)->cqh_first = (elm);                                         \
        else                                                                   \
            (listelm)->field.cqe_prev->field.cqe_next = (elm);                 \
        (listelm)->field.cqe_prev = (elm);                                     \
    } while (/*CONSTCOND*/ 0)

#define CIRCLEQ_INSERT_HEAD(head, elm, field)                                  \
    do {                                                                       \
        (elm)->field.cqe_next = (head)->cqh_first;                             \
        (elm)->field.cqe_prev = (void *)(head);                                \
        if ((head)->cqh_last == (void *)(head))                                \
            (head)->cqh_last = (elm);                                          \
        else                                                                   \
            (head)->cqh_first->field.cqe_prev = (elm);                         \
        (head)->cqh_first = (elm);                                             \
    } while (/*CONSTCOND*/ 0)

#define CIRCLEQ_INSERT_TAIL(head, elm, field)                                  \
    do {                                                                       \
        (elm)->field.cqe_next = (void *)(head);                                \
        (elm)->field.cqe_prev = (head)->cqh_last;                              \
        if ((head)->cqh_first == (void *)(head))                               \
            (head)->cqh_first = (elm);                                         \
        else                                                                   \
            (head)->cqh_last->field.cqe_next = (elm);                          \
        (head)->cqh_last = (elm);                                              \
    } while (/*CONSTCOND*/ 0)

#define CIRCLEQ_REMOVE(head, elm, field)                                       \
    do {                                                                       \
        if ((elm)->field.cqe_next == (void *)(head))                           \
            (head)->cqh_last = (elm)->field.cqe_prev;                          \
        else                                                                   \
            (elm)->field.cqe_next->field.cqe_prev = (elm)->field.cqe_prev;     \
        if ((elm)->field.cqe_prev == (void *)(head))                           \
            (head)->cqh_first = (elm)->field.cqe_next;                         \
        else                                                                   \
            (elm)->field.cqe_prev->field.cqe_next = (elm)->field.cqe_next;     \
    } while (/*CONSTCOND*/ 0)

#define CIRCLEQ_FOREACH(var, head, field)                                      \
    for ((var) = ((head)->cqh_first); (var) != (const void *)(head);           \
         (var) = ((var)->field.cqe_next))

#define CIRCLEQ_FOREACH_REVERSE(var, head, field)                              \
    for ((var) = ((head)->cqh_last); (var) != (const void *)(head);            \
         (var) = ((var)->field.cqe_prev))

/*
 * Circular queue access methods.
 */
#define CIRCLEQ_EMPTY(head)      ((head)->cqh_first == (void *)(head))
#define CIRCLEQ_FIRST(head)      ((head)->cqh_first)
#define CIRCLEQ_LAST(head)       ((head)->cqh_last)
#define CIRCLEQ_NEXT(elm, field) ((elm)->field.cqe_next)
#define CIRCLEQ_PREV(elm, field) ((elm)->field.cqe_prev)

#define CIRCLEQ_LOOP_NEXT(head, elm, field)                                    \
    (((elm)->field.cqe_next == (void *)(head)) ? ((head)->cqh_first)           \
                                               : (elm->field.cqe_next))
#define CIRCLEQ_LOOP_PREV(head, elm, field)                                    \
    (((elm)->field.cqe_prev == (void *)(head)) ? ((head)->cqh_last)            \
                                               : (elm->field.cqe_prev))

#endif /* sys/queue.h */
